minor #20626 Tag missing internals (ogizanagi)

This PR was merged into the 2.7 branch.

Discussion
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Tag missing internals

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        | N/A

Commits
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97e94b4 Tag missing internals

Author: nicolas-grekas

Core/Authentication/RememberMe/PersistentToken.php

@@ -12,9 +12,9 @@
 namespace Symfony\Component\Security\Core\Authentication\RememberMe;
 
 /**
- * This class is only used by PersistentTokenRememberMeServices internally.
- *
  * @author Johannes M. Schmitt <schmittjoh@gmail.com>
+ *
+ * @internal
  */
 final class PersistentToken implements PersistentTokenInterface
 {